Water Transfer Systems for Fresh Water Supply in Germany A.H. Schumann, Institute of Hydrology, Water Management and Environmental Techniques, Ruhr-University Bochum, 44780 Bochum, Germany 1. Introduction In general, water is no limiting factor for the socio-economic development in Germany. The total amount of 164.000 mio m³ of renewable water resources is used to less than 28 percent. For fresh water supply only 6.400 mio m³ water is used per year (Naber, 1996). Nevertheless, water transfer systems became necessary in the last 150 years in many parts of Germany and will also be needed in the future. There are mainly four reasons for establishing water transfer systems for fresh water supply: to bridge the gap between demand and supply by a transfer from regions with a surplus of water to regions with unfavourable hydrological conditions and/or high demand, to improve the local water supply conditions, which are affected by pollution of local water resources, to stabilise the public water supply in periods with a maximal demand, to improve the economical conditions of water supply systems by the cost-average effect in large units. —

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In the following, some large water transfer systems which are operated since some decades in Germany are presented. The aim is not to discuss their technical characteristics or parameters, but the reasons why these systems were built, as well as some experiences and problems of their operation, which were depends mainly from the specific relationship between donor and recipient region. It will be shown that problems of operation result mainly from unexpected economic developments and from growing environmental concerns of a changing societal perspective. 2. Large fresh water transfer systems in Germany 2.1 General remarks The yearly precipitation for Germany is rather uneven distributed. In some mountainous regions the yearly precipitation values above 900 mm are measured but other more continental influenced regions receive only a precipitation below 500 mm. There exists a general task for water transfer systems in Germany to supply large cities, which are situated in regions with low precipitation with fresh water. Water transfer equalise here the differences between a high local water demand and a limited availability of local water resources. Many water transfer systems were built to supply large cities such as Munich, Stuttgart, Frankfurt, Cologne or Leipzig. Another reason for water transfer are water quality problems. More than 80 percent of the fresh water supply in Germany is based on groundwater. The groundwater resources were affected by pollution during the time of fast industrial developments and are still under pressure of a continuing pollution by agriculture and by leakage of urban drainage systems. The Environmental Agency in German made an assessment in 1989 that the nitrate concentration of groundwater recharge is only for 15 percent of the agricultural used areas of Germany below the threshold for fresh water (50 mg NO3 /l) (UBA, 1989). The agriculture in Germany can be characterised by an unbalanced utilisation of nitrogen fertilisers. In 1950, the total amount of nitrogen fertilisers used per hectare and year was 60 kg, in 1985 200 kg. The total demand of the agricultural areas can be assessed with 100 up to 150 kg/ha and year. In total, a yearly surplus of 60 to 100 kg nitrogen per hectare and year remains on agricultural 1

used areas (Mehlhorn & Röhrle, 1990). This situation force in many regions of Germany the transfer of water with low loads of nitrate to regions with higher nitrate concentrations in the groundwater. In general, we can identify three reasons to establish water transfer systems: - the hydrological conditions which limit the availability of water resources, - the local centres of demand in form of large cities, which can not be supplied from local resources, - water quality problems which force to also use water transfer in order to make local water resources useable or to replace them. In fresh water supply dilution is still used as a solution for pollution. In the following, some fresh water transfer systems are discussed: (1) the water transfer systems from the Harz Mountains, (2) the water supply system of the Rhine-Main Region with the financial and industrial centre Frankfurt and (3) the Lake of Constance water transfer system.

(1) (1) (2)

(3)

Large Fresh Water Transfer Systems in Germany (from Mehlhorn & Weiß, 1994) (1) Harz Mountains Transfer System, (2) Water Supply System Rhine- Main, (3) Lake Constance Water Transfer System 2

2.2 Water Transfer from the Harz Mountains Caused by orographic effects the Harz Mountains receive a yearly precipitation between 1200 to 1400 mm. In the rain shadow of these mountains the precipitation values range between 500 and 700 mm. The Harz Mountains have a high importance as a source of fresh water in a relatively dry region. The mountains are used as a donor region for two different water transfer systems which supply regions in the north- west and in the east. The western water transfer systems was built up in different steps between 1928 and 1969 (Schmidt, 1967). Today, it consists of 6 reservoirs with a total storage capacity of 183 mio m³ and a transfer system with a length of 416 km in total (Harzwasserwerke, 1998). The first pipeline over a distance of 200 km was built in 1934 to supply the city of Bremen with fresh water. It became necessary as the local water resources in the river Weser were polluted by the potash industry. The utilisation of local groundwater resources around Bremen is limited by a possible intrusion of salt water from the North Sea. During World War II, the Volkswagen-plant in the city of Wolfsburg became the second important water user within this systems. This industrial complex was built in a region with an insufficient quality and quantity of water resources. Since 1943, Volkswagen was supplied via a 80 km long pipeline from the Ecker-reservoir, which was completed in 1942 (Schmidt, 1967). In the meantime, also the city of Hannover was supplied from the Harz region and today also the city of Göttingen in the south of the Harz Mountains depends from this transfer system. After World War II, also some groundwater works were integrated into the supply system. New reservoirs were built and connected by 65 km and 37 km long pipelines. This water transfer system was developed in a time with less environmental concerns and without public decision-making process. Nevertheless, the reservoir system which forms the source of the transfer system is highly accepted today. This results mainly from the other objectives of reservoir management: the flood protection, which is very effective for the valleys downstream of the reservoirs, the great importance of the reservoirs for recreation and tourism (three of the six reservoirs can be used for swimming and water sports). — —

After some decades of management, the environmental and ecological conditions have been adapted to the changed hydrology. Nevertheless, each change of the existing system in future would be restricted by environmental concerns. The water authority which manages the reservoir system is under public pressure to improve the ecological conditions by an environmental sounded operation and changes of existing control structures. (e. g. with fishpaths). After the World War II in the eastern part of Germany, the water demand in the industrial region of the cities Halle, Leipzig and Bitterfeld was growing very fast. As the local water resources were affected by pollution from the chemical industry and by open-cast working lignite mines, it became necessary to establish a water transfer system from the flood plains along the river Elbe into this region. During the war along the Elbe river, large groundwater works were built to supply arms industry. After the war, this unused capacity could be transferred in this industrial region to satisfy a growing demand. Since 1938 also a reservoir system was planned in the eastern part of the Harz Mountains with three main objectives: fresh water supply for the industrial region Halle/Leipzig, flood protection and low flow augmentation. This system was completed in 1959 and connected with the water transfer system from the Elbe river through a pipeline with a length of 124 km. Today, this system supplies 3.5 mio inhabitants with nearly 90 mio m³ fresh water per year. It is remarkable, that a decrease of the industrial demand after the re-unification in Germany reduced the total demand from 170 mio m³ in 1989 to 90 mio m³ per year today (Foltan, 1996). Nevertheless, the existing capacities will be used also in the future as communities southwards from the city 3

of Leipzig will be supplied which are affected by an anthropogenic disturbed groundwater situation caused by lignite mining. Within this water transfer system the use of two different sources for fresh water ensures a high quality and a stabile supply. Remarkable here is the unexpected reduction of the demand which led to a temporal unused capacity. This capacity can be used in future to improve the fresh-water supply in other regions in a very effective way. 2.3. The Water Transfer System of the Rhine-Main Region This system serves mainly for a water supply of the conurbation of the Rhine-Main area. The population density of this area is very high with 1322 inhabitants per km². On 7.6 percent of the federal state of Hessen live 37 percent of its inhabitants. The yearly precipitation in this region is 670 mm, which is below the German average. The total water demand much higher than the groundwater recharge (in average 186 percent). The water supply for the urban region is based on water transfers from the surrounding highlands but also from the lowlands along the Rhine valley. The development of this system became necessary by water quantity and quality problems as the local groundwater resources were affected by industrial wastes. In one of the main donor regions in the lowlands of the so-called “Hessische Ried”, an area of 1240 km² with 800.000 inhabitants an overexploitation of the groundwater became obvious in 1990 (Binder et al. 1999). In this region, which was in former time a wet flood plain of the river Rhine, in 1925 lived only 172.000 inhabitants. At this time, there was a need to drain nearly 40 percent of all agricultural areas in this region. After the construction of dams and dykes against the river Rhine and a drainage of this area, the water problems of agriculture were shifted into another direction. It became necessary to irrigate. Today 428 km² of this region are used for agriculture and 331 km² of this area is irrigated by sprinkling. For fresh water supply within this region and for a transfer to the Rhine-Main area, the groundwater abstraction was increased from 40 mio m³ per year in 1960 to 160 mio m³ per year in 1976 (AG Wasserversorgung, 1992). As a result of this development, the groundwater level was lowered by 2 metres. In the dry year of 1976, the groundwater level dropped further and damages forests and other biotops became evident. In the dry period from 1990 to 1993, also buildings in this region were damaged by sinking. During the wet period from 1977 to 1988, the total available renewable water resources for the Rhine-Main Region were assessed with 406 mio m³/a (AG Wasserversorgung, 1992). This assessment was corrected to 378 mio m³ in 1990 and reduced to only 316 mio m3 in the year 2000 (AG Wasserversorgung, 1994). The total demand in 1990 was estimated with 387 mio m3 per year and for the year 2000 an assessment was made with a demand of 399 mio m³ in a normal year and 420-430 mio m³ in a dry year. Resulting from this growing deficit and considering the conflicts between local demand and water transfer, the management of the groundwater resources in the donating region was analysed in a holistic way. In a general management scheme for the groundwater, its further utilisation was discussed under consideration of the following characteristics (Binder et al. 1999): the efficiency of groundwater use in terms of national economy (e.g. economic damages of changes in the groundwater level, costs and benefits of a reduction of demand, additional costs of changes of the water transfer by utilisation of other sources), the environmental quality (e.g. changes of the ecological value of landscape, including the rivers), the regional development (e.g. changes of the local income, of the employment rate, the local development condition for industry and settlements), the social welfare (e.g. changes of the possibilities for recreation, changes of the agricultural use and the incomes of farmers)

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The resulting masterplan became part of a changed water policy strategy for the whole region in which three developments were initiated: 1. The existing options to protect local fresh water resources in the Rhine-Main Region were analysed to stop further contamination of groundwater and to redevelop local abstractions. 2. A campaign to reduce the demand of fresh water by new technologies and a better understanding of water supply problems, including a reduction of water losses, was started. 3. New resources were developed, especially by artificial infiltration of surface water along the Rhine, was initiated. The total water balance of the city of Frankfurt in 1993 showed a reduction of the total demand of 25 percent, related to 1977, which was caused mainly by a reduction of the industrial demand (AG Wasserversorgung, 1994). In general this example shows that shared water resources which should be managed in an integrated way. Problems of a growing deficit and significant damages in the donor area could be avoided by an holistic analysis of the demand and supply conditions and a balancing of supply and demand which should be based on a extreme hydrological scenario. In the planning process of future water management, the need to reduce the abstraction of water for transfer became evident as a precondition for regional development in the donor region. 2.4. The Lake of Constance water transfer system This system is used for a water supply for 3.4 mio inhabitants with an average amount of fresh water of 130 mio m³ per year (Naber, 1996). This system supplies not only cities like Stuttgart, Tübingen or Heilbronn, but also many small communities in the rural areas in the rain shadow of the Black Forest Mountains. In total 174 communities are supplied. In many cases, transfer system is used only to stabilise local water supply system in critical hydrological periods and to improve the fresh water quality. Fortunately, this system has only a very small impact on its donor area as it uses water from a large natural reservoir. The abstraction of water causes a reduction of the discharge of the river Rhine at the outlet of the Lake of Constance of only 1.2 percent. If the total capacity of the system would be used, just 2.2 percent of the average yearly outflow could be abstracted. Nevertheless, there is a public discussion about possible negative effects on the water level of the lake, which was stimulated by some dry years in the early nineties. It can be shown that such fluctuations are part of the natural variability, but this question is discussed over and over again. Less discussed are some positive side effects of the utilisation of the lake for fresh water supply. One of them is the intensive analyses of its limnological conditions. Other effects are many initiatives to reduce the entry of nitrogen, phosphorus and other chemical substances which were started in the past and which had considerable success (Naber, 1996). The Water Transfer System of the Lake of Constance is an example how economic purposes can be also incentive to improve ecological conditions. 3. Summary - Future problems for water transfer in Germany In Germany, centralisation of fresh water supply is continuing. In 1987, 23 percent of the fresh water was transferred and not used directly. In 1991, this amount was increased to 30 percent. New standards of water quality resulting from the European Commission’s periodic directives will be the driving force to accelerate this development also in the future.

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The water transfer systems which were presented here were mainly developed in a time without concern about possible environmental impacts and without a public planning process. Today of course such conditions do not exist anymore. There is a growing public concern about the possible environmental impacts of each water abstraction. But there is also a general insufficient willingness to share local water resources with other regions, which plays a fundamental role in public discussions. In general, a declining public acceptance of water transfer in the donor region will be the main problem for water transfer in the future. Within the public discussion of such measures two main points play an important role: Are there alternatives to use other sources for fresh water supply ? Will an abstraction of water cause negative effects for the donor region or limit their further economic development ? — —

Water managers which were strongly involved into such discussion recommend the following planning strategy for a water transfer system: An early public information campaign needs to ensure an open public discussion of the measure in the affected region. The arguments for a water transfer should be presented objectively. The reasons for deficits between demand and supply in the recipient region should be explained together with alternatives for water supply from other sources. The advantages and benefits for the donor region should be demonstrated. This could be e.g. improvements of the local infrastructure, e.g. by a new drainage and waste water treatment system. The donor region should be included in the planned fresh water supply system under favourable conditions. In cases, where a transport of fresh water is planned waterworks in the donor region could be used also to supply neighbouring communities with fresh water. —

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Many large water transfer systems in Germany have been operating successfully for some decades for fresh water supply. Especially multi-objective systems with beneficial effects for the donor region (e. g. reservoirs which are used for flood protection or recreation) are highly accepted. Problems exist in such cases where the need for a concerted management of shared water resources between local needs and the demand to transfer is not considered. Here the monitoring of hydrological and demand conditions and the planning of their further development is most important. References: AG Wasserversorgung Rhein- Main (1992) Wasserbilanz Rhein- Main 1990- 2010 AG Wasserversorgung Rhein- Main (1994) Wasserbilanz Rhein- Main 1990- 2010, Fortschreibung 1991 bis 1993 Binder, K. G.; Fuchs, R.; Heinzelmann-Ekoos, T.; Klaus, J.; Michel, B.; Quadflieg, A. ; Solveen, D.; Wurster, H. (1999) Mehrdimensionale Bewertung der Grundwasserbewirtschaftung am Beispiel des Grundwasserbewirtschaftungsplanes Hessisches Ried, Wasser & Boden, 51, 3, p. 19-28 Foltan, W. (1996) 50 Jahre Fernwasserversorgung für den mitteldeutschen Raum, WWt, 6, p.18-24 Harzwasserwerke (1998) speichern , aufbereiten, transportieren, information material 6

Mehlhorn,H.;Röhrle,B. (1990) Die Nitratbelastung der Grundwasservorkommen und Maßnahmen zur Reduzierung der Belastung, Wasserwirtschaft 80 (1990) H.10 Mehlhorn, H.; Weiß,M. Überregionaler Wasserverbund und Fernwasserversorgung technische Möglichkeiten und Erfordernisse, in “Ausgleich und Verbund in der Wasserversorgung”, Bericht aus Wassergüte- und Abfallwirtschaft, TU München 1994, Nr. 119, p. 139- 164 Naber, G. (1996) Fernwasserversorgung, Verlag Oldenbourg, München Schmidt, M. (1967) Die Talsperren im Westharz und ihre Aufgaben, Wasser & Boden, 19, 10, p. 315- 316

UBA (1989) Daten zur Umwelt 1988/89, Umweltbundesamt, Erich Schmidt Verlag GmbH & Co., Berlin

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